Check FET orientation, are you using an alternative op amp? i do believe that there is more of a difference between the rat and rat 2 then just the clipping section, just MHO, but i could be wrong. http://www.analog.com/static/imported-files/data_sheets/OP07.pdfhttp://www.ti.com/lit/ds/symlink/lm308-n.pdfOP07 is not pin to pin equivalent with LM308. Also it is worth to play with the clipping section in the basic Rat layout, as that can really give you different tonality. Yeah, my build acts exactly the same way. Call it good. By the way, I'm not a ProCo Rat guru. Here's a collection of vero (stripboard) and tagboard guitar and bass effect layouts that we have put together covering many classic and popular effects in growing numbers. Thanks. I guess you can verify it. I checked for solder bridges, what super obvious thing am I missing? to get an idea from the available images and the Box comments. After some playing around we decided to use a 1nF cap instead of the 3.3nF, that gives you a much more useful tone/filter range too. I went back through it tonight, everything checks out, I even compared it to the last build I did. Did anyone experience the same / found a solution? No one has noticed that the 560R and 47R should be swapped around to be correct to the original pedal. The one going from input to ground (the one on the left) is just a pulldown resistor, so that won't make a big difference. Double, triple check all your cuts and layouts. But still I get a bit of sound drop/cut on power chords.I replaced the 1uF electrolytic with 100uF; the 2.2Mohms with 1Mohms and will soon try the 220K. i know there is a lot of sonic differences between the rat and rat 2, so the things you're seeing could be the reasons. So I built this the other night with only a few changes. Hi Zach and thanks for your comment :) What makes you believe that rat 2 is not set up this way? Rat 2, Vintage Rat, Turbo Rat, Bratt all quote 1k output impedance without seeing the schematic it's hard to say it belongs there. Thing is such a beast. Played with this some more. Has anyone found a solution? Thanks a lot for any help! There is no straight on replacement for LM308, so to get your circuit working right, you'll need LM308 chip. This maybe the cause of the squeeling some people have noted when nothing is plugged into the input. The origins of the Pro Co "The RAT" can be traced back to the mid-1970s, when Pro Co engineers Scott Burnham and Steve Kiraly repaired and hot-rodded existing distortion pedals, such as the Dallas Arbiter Fuzz Face.Burnham decided he could build a superior product from the ground up, and designed "The RAT… I either messed up a cut somewhere or one of the caps I didnt replace is faulty. Was I wrong? of the Rat. ; The big C 7 is just a coupling capacitor which removes DC content and connects the op-amp to the diodes stage. Also can anyone tell me the cap between pin 3 & 4 What exactly does? The 22nF is the input cap, the 100pF is a lowpass for the distortion and cuts off the high end of the distortion smoothing/softening the clipping making it less harsh. I built this pedal according to the layout and it worked fine but I got a squealing sound when I stopped playing/strumming, adding the 1nf cap removed this squealing noise. Please help, Anyone. Thanks for the layout ! With the information so far, only Works great for me. Just skimming through the comments, i think ill try to add the cap between leg 3 of the IC and ground also to see if this helps. Other unknown pieces are are the actual FET/Transistor If you're looking at the same schematic I just did, there's a 1nF cap from pin 3 to ground, which is what pin 4 goes to as well. From Schematic to Stripboard September 2012 © http://tagboardeffects.blogspot.com Updated 23rd September 2012 A lot of people have asked... A few people have commented on posts asking about offboard wiring. Thanks so much for this summation, definitely going to make these changes soon. Now, there is only couple of small changes to the output buffer and volume control when compared to the original Rat. Given the chance, I cannot even start telling you how great your work is. Good for you, Liam!Did you test the circuit out of the box or straight closed into it with all the offboard wiring? Did another build, it fired right up. The other things you mention are common mods done to the rat to control the frequencies affected by the distortion, I think it's call the Ruetz Mod, so more or less bass. Only way I could get rid of the squealing when gain gets to noon. I also put in switch for clipping selection, 1-RedLED/RedLED; 2-BlueLED/Zenr-Zener; 3-Si-Ge/Si-Ge.The RedLED/RedLED is not lit when I use it but has sound. The circuit is different to the original. The Brat is a low cost unit, many say it doesn't sound as good as the Vintage. quick question, does the resistor change for turbo version apply to dirty rat too or is that 2m2? If you use a 308 and still get the squealing try putting a buffered pedal in the chain. It sounds great, but my distortion control is working as volume control. Give your opinion, If you had a handful of diodes 1n270, as you implement these on the circuit? I got a question, where to wire toggle switch from the board for clipping, if you want to make a switch for multiple clipping, remove D1 and D2 and put two cables from toggle. The cap you added is a 1nF on the actual RAT and is missing off this build. The original seems to be OK but the others seem to have contradicting the Turbo Rat shows the use of Bipolar transistor buffers, are there any Both the Rat 2 and Turbo Rat circuits show 220K input impedances, this disagrees with the Proco's 1M input impedance spec. ITT and 4 Was the only letters written on them. What have you done to get rid the feedback? Take a break, and come back to it fresh. There are two 2.2m's on the board. Any Ideas? Hi, I've just build this board, but got several problem at first. (Skipped 15nf because I couldn't find one at the time) I'm not sure how much gain this has taken away from the pedal but it still sounds fat with a fuzzy-ish gain (LM308). You should still be able I used the OP07, 2n5457 and a 1.5K instead of a 1.6K from the filter pot. Replaced the diodes with blue leds and it roars. information, GFR who confirmed the Turbo Rat and Rat 2 schematics (I think he actually I'm not sure why. I m grateful!Kind regards :). Just remove D1 & D2, take a wire from where one side of D1 (or D2) to a switch (pin2) and another wire from where the other end of the diode was to the switch (pin 5).Place your diode choices across pins 1 and 4, and 3 and 6 for a DPDT switch and hey presto.Use this link for an examplehttp://tagboardeffects.blogspot.co.uk/2014/05/blakemore-effects-rous.html. Also I bought a couple of gold bonded Oa47 for next proyect. Increase that cap value in case you face lots of noise, at the expense of decreasing the max gain available :P. I just finish building a second one of these and it's really gated, like, I get sound if I hit the strings then it cuts out. I haven't found any schematics showing it any other way... Swapping the resistor values would give you a 721Hz and 129Hz pair of low pass filters instead of 1539Hz and 60Hz - and this filters the input to the opamp (see here : http://www.electrosmash.com/proco-rat). I also use a shielded coax pickup lead wire to go from the foot switch the vero board for the input, with the braided side grounded once (i.e. Built it and all functions work. Had to put a 22nf cap from pin-3 of chip to ground. I have implemented the original rat version from your vero layout and the pairs there are also the opposite way than what appears here. Try the other one. The circuit will need tweaking for it to work properly with OP07 (or any other single opamp). on most RAt 2 schemes seems that 2.2M from the left is replaced with 1M, I will try that change as well to low as 220k. Did Anyone build the Rat with another IC like TL071 or similar ? mine is squealing in a insane way, when the cable is unplugged. HI. If you want to turn this in to Turbo Rat, then just swap the 2M2 resistor for 220K and use 3mm red LEDs for clippers. Rat 2, Vintage Rat, Turbo Rat, Bratt are later/current models. footswitch. I'll check my values. My guess is this unit uses it's own variant of the circuit, but is close It still fits very comfortably into a 125B.I also added a switch that toggles between yellow diffuse LEDs and the stock silicon clipping diodes... and I'm glad I did, because I prefer the LEDs.Finally, I implemented the "Lube" mod from Beavis Audio and put the 560r resistor on an on/off switch.All mods highly recommended. what you could do is take the rat 2 layout as it is and put sockets in place of the resistors and swap them to be like the original, or it gives you the ability to try different values and see what you like. And while i m at it, you might want to use a larger value for that cap in case you are facing lots of noise, at the expense of reducing the gain :), Yes, had to use a 22nf :( Now I can max gain though :). I got the squeal that somebody else got. Hey guys I have a proco rat distortion and I would like to mod it by adding a 3 way toggle switch like jhs mods ha and my questions is where do conect or witch componnent to remove to add my toggle switch.